AKRON, OHIO (Oct. 27, 3 p.m. ET) — North American polypropylene resin prices have plummeted an average of 14 cents per pound since Oct. 1, with polyethylene prices taking a smaller, 3-cent drop since then as well.

The PP swoon ends a two-month period in which prices were flat. Prices for the material had tumbled a total of 19 cents per pound in June and July. That drop came after the market was besieged by a total of 37 cents in increases from January through May.

The October decline means 34 of the 37 cents in increases have disappeared — and it reinforces the PP market’s reputation for extreme volatility.

North American PP demand has been soft for most of the year, and that weakness finally caught up with prices for propylene monomer feedstock, according to PP buyers contacted by Plastics News. Ongoing economic uncertainty caused sales of PP into areas such as consumer products — including furniture and housewares — to be down 11 percent through July, according to the American Chemistry Council in Washington.

Overall, North American PP sales were down almost 7 percent through July, with an 18 percent drop in exports worsening a drop of 6 percent in domestic sales. Buyers said an additional PP price drop in November is a strong possibility as the market moves into the traditionally slower fourth quarter.

The picture in the North American PE market is more blurry. After two flat months — and with demand slack at best — buyers reported the 3-cent drop for October. Some reported drops of 5 cents on high and linear low density PE and of 6 cents on low density PE, but the majority had reported the 3 cents as of Oct. 26.

Some buyers added that they were trying to win additional reductions. But a PE buyer in Texas said suppliers “are up in arms and viciously trying not to let the market go down the 5.”

The Texas buyer added that PE makers are trying not only to stem the tide, but to reverse course and push through a 5-cent increase for November.

Mike Burns, a PE market analyst with Resin Technology Inc. in Fort Worth, Texas, said the North American PE field was oversupplied in September and October, especially with demand checking in as average or weak.

“There was too much resin available at a low cost to produce,” he said.

Burns added that PE makers’ profit margins are tightening at a time when inventories are high, which should create a November market that he described as “interesting.”

U.S./Canadian PE demand has muddled its way through 2011. HDPE sales were up almost 3 percent through July, according to ACC, and sales of LLDPE were up almost 1 percent. Sales of LDPE in the region hadn’t fared so well in that time frame, dropping almost 1 percent.